Prion diseases occur in infectious, hereditary, and sporadic forms. Altered conformation of the prion protein (PrP) plays a central role in the pathogenesis of these disorders. My objective is to understand how altered conformations of PrP arise and produce disease. My strategy is to express mutant PrP genes in scrapie-infected neuroblastoma cells and mice, and to study the changes induced by these mutations with biochemical, pathological, and immunological techniques. Two interesting disease models have been generated in preliminary deletional mutagenesis studies: a small infectious prion which can be solubilized in its native state (PrPSc106), and a hereditary neuronal storage disease. In this proposal, I describe how I plan to investigate these disease models further. I will exploit the solubility of PrPSc106 to study the mechanism of prion replication directly. Starting with PrP106 as a minimal backbone, I will investigate the importance of specific PrP epitopes for prion replication, species specificity, and strain properties. Finally, I will determine whether mutant PrP neuronal storage diseases are triggered by protein misfolding or by aberrant retention in the endoplasmic reticulum.